FUSELAGE
With a balsa stripper, strip 1/8-inch wide strips from 3/16th by 36 or 48-inch balsa and pin fuse top and bottom strips to the plan. Note the extra 1/8 by 3/16 strip glued at the wing saddle area. Cut and glue the former and diagonal strips in place. Take care to fit these as closely as possible to get a close glue joint. Remember there is a 3/16th sheet firewall/nose block to be glued onto the nose, so don't confuse this piece as a fuselage sidepiece in the plan side view.

Cut two rear stab support pieces from 1/8th sheet with the grain horizontal and glue to the fuselage side between former F6 and the tail. Cut triangles of 1/8th balsa as shown on the plans. Decide what you wish to use to hook the wing hold down rubber bands onto. I used skewers from the supermarket, while some builders have used nyrod and similar materials. Before gluing these triangles into place, stack them and drill appropriate sized holes.

Remove the first fuselage side from the plan and build the second with the same methods. The finish fuselage side will feel pretty flimsy at this point, but when assembled with cross pieces it makes for a strong and light structure.

Build formers F2 and F4 over the plans using 3/16th square balsa stripped from 3/16th sheet. Glue both formers to one fuselage side aligning carefully with a square. Glue directly on top of the F2 and F4 1/8th side pieces already in place. Remove this side from the plan and place it (and the glued F2 and F4 formers) upside down over the plan top view. Lightly pin both F2 and F4 formers in place on the plan. Since the fuse sides are straight from the nose right back to F4 it is a simple matter to align and glue the second fuse side in place.

Cut the nose/firewall from 3/16th sheet and drill the motor and cooling holes. I used forstner bits for this. The motor hole should be cut slightly undersized and sanded gradually to fit your motor's gearbox. The whole firewall should also be cut from the sheet slightly oversized to allow a bit of extra area for alignment purposes when installing.

Pull both fuse sides together, aligning carefully over the plans. Use a small piece of 3/16th square between the sides at the very rear to space the side's 3/16th apart. This piece should extend from the fuse bottom just to the top of the stab support piece. This allows for proper fuselage spacing when fitting the fin later. Glue the rear stab top and bottom pieces in place making sure they fit flush with the top and bottom.

Cut 3/16th square balsa pieces to fit across the fuselage top at formers F5 and F6, sanding the slight fuselage curvature into the ends before gluing. Note that formers F5 and F6 consist of 3/16th square pieces added during final assembly unlike F2 and F4 which are completed separately. The upright sidepieces of F5 and F6 are actually the fuse side formers built into the fuselage earlier. Remove the fuselage from the plan and turn upright. Cut and glue 3/16th square sticks in place at formers F5 and F6 on the top side also.

Cut the top fuselage nosepiece (F10) slightly oversize. Cut the two cooling holes. The size should be about 7/8th inch. Note the cooling holes here, in the nose block, and on the bottom fuse nosepiece are necessary for proper motor cooling. Operating without these inlet and exit holes will result in hotter running motors and shorter motor life.

Glue the top fuse nosepiece in place after test fitting and sanding for a snug fit. Do the same with the fuselage nose bottom piece (F9). Note that both are cut from 1/8th sheet balsa. I installed the balsa cross grain on the bottom. The top piece has the grain running along the fuse and this has proven plenty strong.

Find a strip of scrap of 1/6th balsa about an inch wide (slightly wider than the fuselage) and sand the bottom to about a 45-degree angle. Lightly score one side of the piece and bend it carefully without breaking. This forms the fuselage windshield area. Glue across the fuselage top in front of the wing saddle area. The position is not critical and has been varied quite a bit in several of the prototypes making each plane look slightly different. Sand or plane the top of this piece so that it is the same height as the fuse at the wing saddle. Cut off any extra at the fuselage sides as well. A small piece of 1/16th is used to cap the cabin area from the windshield back to the wing saddle opening. Simply place the piece on top so that a straight edge lines up with the wing saddle at the back and then trim away at the windshield area. Small scraps of balsa can be placed on the sides as well.

If you will always hand launch the Robin, there is no need to install landing gear. However, if you wish to enjoy it in a paved parking lot (under the lights at night is great fun) now is the time to install ¾ inch strips of 1/32nd ply across the fuselage as shown on the plans.

WING CONSTRUCTION

Note: the wing is built in two pieces side by side on the plan.

Cut 14 1/16th balsa wing blanks, align them in a stack and tape lightly together. Tape the wing outline from the computer printout to the rib stack and cut the ribs using the hacker of your choice. Sand the ribs in a stack to remove saw irregularities.

Strip wing spars (3/16th square) from 3/16th balsa, ensuring the grain is pretty straight and there are no imperfections, which could compromise spar strength. Pin the two lower spars to the plan. Cut two pieces of 1/8th balsa one inch wide and pin to the plans as shown to form the wing trailing edge. Align the ribs over the plan, and glue in place all ribs EXCEPT the two center ribs. Leave these unglued, as they will be lined up when joining the wing halves with the proper dihedral.

Install and glue both top spars. Again DO NOT glue at the center ribs. Use a strip of 3/16th balsa to make the wing leading edge. Glue in place.

Using the computer printout cut the wing tips from 1/16th sheet balsa. The lightening holes probably don't remove much weight, but they look cool and should be used. Sand the tips smooth and glue to the outer rib on each wing panel. Install the tip supports (1/8th balsa).

The one difficult spot in the wing construction is the sanding of the wing trailing edge to an airfoil shape. I removed both wing halves from the plan and placed them close to the edge of my workbench so a sanding block could be used easier. Be careful not to damage the rear of the ribs when sanding. The trailing edge does not need much removed; in fact a final thickness of about 1/16th inch is fine.

While the panels are off the workbench sand or plane the 3/16th balsa leading edge to the airfoil shape shown on the plan.

To join the wing halves use blocks 2 inches thick placed under the both wingtips. First locate one panel back over the drawing with the dihedral block under the tip. Then using a square align inner rib 90 degrees to the work surface and 90 degrees to the wing leading edge. You will need to sand a small amount of angle in both the top and bottom spars. Remove this wing half and do the same with the other wing panel. Now you should be able to place both panels back over the drawing. And glue the two center ribs together. Cut the 1/32nd ply dihedral brace and after cutting through the two center ribs immediately in front of the spar with a razor saw or similar, install and glue the plywood brace into place.

Build both the stabilizer and fin over the plans using the computer printout to cut out the sheet pieces. Do the same for the rudder and both elevator halves. Note that the elevator leading edge is actually one continuous piece of 3/16th balsa and is the easiest and lightest way to allow both elevator halves to work with one pushrod. Sand all assembled elevator and fin parts before assembly. On the prototype I sanded to a thickness slightly over 1/8th inch. Align the fin on the stabilizer to that it is 90 degrees to the vertical as well as 90 degrees to the stabilizer trailing edge. The whole assembly can now be trial fitted and glued in place on the fuselage. You may opt to cover these assemblies before gluing into place. In this case mark the fuselage outline on both pieces and cover just to this line, leaving bare balsa areas for gluing on final assembly.

Bevel both elevator halves on the bottom to allow a hinge movement. I didn't bevel both sides of the rudder; just one and this has worked perfectly. Clear cellophane tape over the entire rudder and elevator hinge lines after final assembly and covering makes for a simple and foolproof hinging system.

Make two control horns from 1/6th ply as shown on the plan and cut 1/16th slots in the rudder and elevator at the appropriate spots (in alignment with the pushrod exit holes). Glue both pushrods into place with Ca.

FINAL ASSEMBLY
Before covering the fuselage install the radio gear. Doing so now makes it much easier as you can reach things through the uncovered sides. Glue a 3/16th square balsa "spar" along each fuse side as shown on the plans. These pieces make up the base for a 1/16th cross grain balsa plate, which will hold the receiver and battery pack near the fuselage floor. The servos are installed on two 3/16th square balsa rails as shown. Wick a drop of ca into the holes drilled to accept the servo screws. Location of the radio gear shown on the plan has worked well. Larger heavier servos might want to be installed in a more forward position. Simply placing the gear on the balsa plate can give a pretty good idea of where things should go.

I use either thick ca (wrap your finger in wax paper) or epoxy (sparingly) smeared over the balsa plate, which seals the wood and allows Velcro to stick strongly. Moving the flight battery fore and aft can easily change the center of gravity. The CG shown on the plans will make for a stable airplane. I personally like the CG a bit further to the rear making the plane more agile in loops etc.

The motor installation is pretty simple. The gearbox is held to the nose block with two small screws. I installed two half-inch pieces of yellow nyrod in the nose block to support the screws. The extra length extending from the nose block inside the fuselage allows the motor to flex slightly which is good if you're belly landing the plane on grass. There is a two-degree down thrust built into the fuselage during construction.

Cover the airframe with a lightweight covering. The prototypes are using clear monocote.

After the wing is covered, using a heat gun twist two degrees of washout into each wingtip.

After covering the complete airframe, run the two pushrods. I use a z-bend at the control surface and an easy connector on the servo. Trial fit without hinging the elevator and rudder and determine the location of the plywood control horns. Cut a 1/6th slit in the leading edge of both surfaces and glue the control horns in place. Now you can actually install the rudder and elevators using clear cellophane tape. I was surprised the first time I saw this used, but it is ideal for these small models. Some brands of tape have finishes, which makes it virtually impossible to see on your nice covering job.

Now is the time to install the landing gear. Bend 1/16th music wire as shown and install using small plastic straps cut from a margarine container or similar. Use very small lightweight screws. Use lightweight foam wheels designed for park flyers. The wire and wheels I use add 1.5 ounces to the airframe, which is about a ten percent increase in weight, about the same as adding a pound to a ten-pound airplane. The addition of wheels in a small lightweight plane like the robin is noticeable in performance and general flight characteristics. The plane is more agile hand launched without wheels. At the same time it is a different but very enjoyable airplane on wheels, especially if you, like me, enjoy touch and goes. If you use the wheels small plywood or wire skid should be glued to the fuse bottom as shown on the plans.

FLYING
I attach the wing with four #33 rubber bands, two on each side. No more are necessary. Without wheels, just pick this little plane up, raise it over your head and give it a little shove straight ahead. It should be released level or slightly nose down as in all hand launches. There is plenty of power and the plane will just fly off. Landings are slow and easy and just a matter of removing throttle as needed and flaring just before touchdown.

Taking off with wheels from pavement is another matter, and is difficult in any wind as even a slight breeze can upset this light airframe when it starts to move, particularly in any crosswind. The trick is to ease on throttle VERY gently and get the tail up and flying. From that point the plane tracks straight and takes off briskly. What is really neat flying from pavement is the touch and goes. I find about 30 percent throttle works well when on final and it's almost like flying in slow motion. Taking off again during a touch and go is not the same as starting from a dead stop. The tail is still up and flying and the plane behaves like it's on rails as long as the flight path is close to being into the wind.

Any questions may be directed to me at astroflyer@rushcomm.ca